Main structure of a stepping exercise machine



FIG. 1 is an upper perspective view of the main structure of a stepping exercise machine showing my design.

FIG. 2 is a side view thereof;

FIG. 3 is an opposite side view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a back view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof; and,

FIG. 8 is an upper perspective view thereof, showing a pedal attachment.

The broken line drawings are intended for illustrative purposes and form no part of the claimed design. 

I claim the ornamental design for a main structure of a stepping exercise machine, as shown and described. 